Can't use "--principal" flag with igwn-robot-get 0.2.0 (only positional argument)

The documentation for version 0.2.0 of igwn-robot-auth says to use igwn-robot-get like this: /usr/bin/igwn-robot-get --principal my/robot/name@LIGO.ORG --keytab /home/user/.secure/robot.keytab, but doing so returns an error:

[detchar@CIT-grid 13:16 ~]$ /usr/bin/igwn-robot-get  --keytab /home/[redacted].keytab  --minsecs 3600  --principal [redacted]
usage: igwn-robot-get [-h] [-V] [-v] [-k KEYTAB] [-c CCACHE] [-a VAULTSERVER]
                      [-i ISSUER] [--credkey CREDKEY] [-r ROLE] [-m MINSECS]
                      [--vaulttokenfile VAULTTOKENFILE] [-o OUTFILE]
                      [--vaulttokenminttl VAULTTOKENMINTTL] [--condor]
                      principal
igwn-robot-get: error: unrecognized arguments: --principal

whereas using the command with the princpal as a positional argument (same as above, but without --principal) does work.